With the advent of close proximity near field communication systems which use the magnetic near field for communication (of which the Near Field Communication (NFC) standard is one such standard), a variety of new applications have emerged that can benefit from this close proximity near field communication systems.
Some close proximity near field communication systems can provide high data rates over a wireless communication channel within a range of several centimeters and enables a user to exchange data between devices by simply performing a sweep, wave or touch gesture of one device in close proximity to another like device or device appropriately enabled.
The high data rates are driven by the need to transfer ever increasing amounts of data over the very short period of time available while the two devices are within close proximity. If the data transfer takes too long, the user experience will be affected as the user will be required to maintain the two devices in close proximity for an extended or an indeterminate period of time.
One of the devices is typically a mobile device such as a mobile phone, and the second device is typically a fixed device—such as a Point of Sale (POS) terminal or powered electronic sign.
In the arrangement described above, the fixed terminal device is typically mains powered and as such has substantially no power consumption constraints. It is considered a master in the system and as a result produces broadcast near field transmissions in the form of a modulated carrier, such that a slave mobile device can detect these signals, wake up from a low-power sleep state and begin communication with the master device. The full data transmission must occur while the communication mechanisms are within communication range.
There are cases where it is beneficial to utilize near field communication between a mobile device and another mobile device. Since the minimization of power consumption is a primary driver in the design of mobile devices, or any battery-powered device, it is currently not practical to have a battery-powered device act as a master as its requirement to continuously broadcast a beacon signal which includes a carrier would place an unacceptable drain on the battery.
To implement the mobile to mobile communication case it is common to initiate and assign a master role to one of the devices by having the user select a menu item, icon, initiate an application, or the like, thus initiating the broadcast near field transmission. Once the near field data transaction (data exchange) has occurred or the system has timed out, the master mode would be exited and the devices would typically resume sleep mode and act as slaves again.
A typical arrangement of a near field system includes two devices as described above. In arrangements that contain many devices, in particular where many devices can communicate with many other devices which may be of varying or unknown types, it becomes impractical to assign one or more of those devices to be masters, especially if the assignment needs to be activated manually.
There are many NFC protocols in common usage and most NFC chips support several of these, for example Felica, Mifare and NFCIP-1 etc. Thus compatibility between master and slave becomes an issue. For example if the master is set to the Mifare protocol and the slave is set to the NFCIP-1 protocol, the devices may not be able to communicate.